Due to many factors including the high cost of labor associated with populating circuit boards with components, technology in the electronic manufacturing arts has developed to automatically place such components on boards. A representative sample of such systems may be seen depicted in U.S. Pat. Nos. 4,202,092, 4,543,713, 4,222,166, 4,528,747, 4,300,715, and 4,451,324.
In a move to simplify the simultaneous positioning of chips adjacent correlative sites of a circuit board, a system was provided by Panasonic National, details of a representative system thereof being set forth in a publication entitled "Specifications: Panasert Simultaneous Chip Component Placement Machine Model NM-8270". With regard to such disclosure and specifically with respect to the details thereof set forth on page 8, a plurality of tubes, each carrying stacked components therein may be loaded directly onto corresponding placement stations within the machine. The circuit board to be populated is thence positioned over the plurality of component tubes. The tubes are arranged in a horizontal pattern corresponding to the horizontal pattern of sites on the underneath side of the board at which the components are desirably to be placed. The underneath site of the board is coated with an adhesive. Upon urging of the stacks of components within their corresponding tubes by means of pushpins or the like, the topmost components of the tubes are thereby urged against the adhesive on underneath side of the board at the corresponding location thereon where the components are desired to be placed. The thus-populated board is then replaced with the next board and the process repeated, resulting in simultaneous multiple chip component placement.
While the aforementioned system does eliminate problems associated with the other hereinbefore cited references including the complexity of robotic arms, relative complex travel paths of the circuit components from magazines or tapes to the circuit board sites, and the like, several serious problems are nevertheless associated with this system. Notable among these are the tendency which components have to stick together when withdrawn vertically from the stacks caused by static, dust, dirt, adhesive, or other particulate matters present on the components and adjacent thereto. Problems associated with this failure of components to uniformly exit the tube and be deposited on the board include jamming of the system and incorrect orientation of the uppermost chips in the tube after deposition on the underneath side of the board in undesired orientations. This, in turn, results in unacceptable rejection rates for the populated boards.
In an effort to alleviate these problems, in our copending U.S. Patent application Ser. No. 07/353,299, which is a Continuation-in-Part of Ser. No. 07/155,945, now abandoned, incorporated herein by reference, a system was disclosed for simultaneously dispensing a plurality of chips from corresponding vertical stacks arranged in a load plate for subsequent downward displacement onto the upper surface of a planar board in a desired pattern.
In such a system, each component was individually stripped from the bottom portion of its corresponding stack of components prior to further displacement downward. In this manner, the aforementioned problem was alleviated of components sticking together when displaced upwards and fixed to the underneath side of a board. However, several additional problems remain with the hereinbefore noted Panasonic system which have been addressed by the present invention.
First, the prior art system has provided a relatively large and complex machine which was, for all practical purposes, dedicated to one pattern of chips and a relatively small chip density or population due to the bulk of the apparatus required for positioning each of a plurality of columns of chips in the desired location in the plane for placement. Changing the pattern and type of chips was an extremely cumbersome and time consuming process requiring large amounts of down time of the expensive machine while it was being reconfigured to a new chip pattern. Moreover, it was still often extremely difficult to accurately align and position chips for placement on the planars. This was due to the extremely minute dimensions of the chips and extreme accuracy required in their placement on the planars in order to properly align with the circuit traces disposed thereon.
Accordingly, a chip placement system was desired for simultaneous multiple component placement which was of a small, simple, inexpensive, and reliable construction for populating high circuit density boards. Such apparatus was further desired which facilitated off-line modification of the chip placement patterns and replenishment of chip supplies to accommodate different product circuit boards and to minimize placement machine down time. Moreover, a modular system was further desired which could readily provide for a multiplicity of such machines arranged in tandem and ready substitution of machines in the system. This would facilitate higher density population of boards wherein due to limited area above a board, mechanisms could not be devised small enough and yet reliable to simultaneously place all such chips in one operation or machine.